Solar output calculator
The output of a solar system is its installed power multiplied by how many kWh each kilowatt-peak produces at your location. Enter both and the calculator gives the annual total and the monthly average.
For a specific address, the EU's free PVGIS tool estimates the output month by month with the real orientation and tilt.
Your measurements
How many kWh one kWp produces per year where you live. The free EU tool PVGIS gives the figure for your address, orientation and tilt.
Result
- Estimated annual output
- 3,000 kWh
- Average monthly output
- 250 kWh
Monthly output varies a lot between summer and winter — the figure shown is the annual average.
How the calculation works
- Annual output (kWh) = installed power (kWp) × specific yield (kWh per kWp per year).
- Average monthly output = annual output ÷ 12.
Worked example
A 3 kWp system with a specific yield of 1,000 kWh/kWp produces about 3 × 1,000 = 3,000 kWh a year — on average 250 kWh a month.
What the calculator assumes
- The specific yield is a long-term average for panels facing south at about 30–35° without shading.
When to adjust the result
- The monthly average hides the seasons: in July a system produces several times more than in December.
- Dirty panels, snow and very high temperatures reduce output; panels degrade by roughly 0.5% a year.
What changes real solar yield
Specific yield (kWh per kWp per year) depends on location, orientation, tilt and shading. The European Commission's free PVGIS tool gives a figure for your exact coordinates and roof, which is more reliable than a national average.
Expect seasonal swings: summer months can produce several times more than winter months. Real systems also lose a few percent to inverter losses, heat, dirt and cable losses, and panels lose a small fraction of output each year — check the manufacturer's degradation warranty.
Frequently asked questions
How much does a 3 kWp solar system produce?
Its power times the specific yield of your location — for example about 3,000 kWh a year at 1,000 kWh/kWp.
Why is winter output so low?
Days are shorter, the sun is lower and there is more cloud and snow, so a system produces only a fraction of its summer output.
How much does a 5 kWp system produce?
Multiply 5 by your specific yield: in central Europe often roughly 900–1,100 kWh per kWp, so about 4,500–5,500 kWh a year.
Do panels produce on cloudy days?
Yes, but much less — diffuse light can give a fraction of the clear-sky output.